The present invention relates to a method of producing color filters by forming a color filter array directly on a rugged substrate consisting, for example, of solid state imagers.
According to the conventional methods of producing color filters, a photosensitive material is coated on a flat substrate made of, for example, a glass, the photosensitive material is exposed through a mask of a predetermined pattern, the development is effected to form patterns, and the patterns are dyed with dyes. The thus obtained substrate with filter has been used being placed on the solid state imagers. With the above-mentioned method, however, when the color filter of fine patterns is placed on small solid state imagers, the thickness of the substrate or the deviation in position when the color filter is being placed makes it difficult to increase the resolution of the camera tube.
If it is attempted to directly form the color filter on the substrate consisting of solid state imagers having rugged surfaces, the ultraviolet rays which are vertically incident upon the substrate during the step of exposure are irregularly reflected through the rugged or stepped portions; the ultraviolet rays proceed in parallel with the substrate up to the inner side of the patterns that are to interrupt the ultraviolet rays, making it difficult to properly shape the patterns. This state is illustrated below with reference to FIG. 1. Ultraviolet rays 2 transmitted through a transparent glass portion 6 of an exposure mask 1 are reflected by a tilted surface 3 of a substrate 7 located beneath the mask 1, and are introduced into a photosensitive resin 5 beneath a opaque portion 4 of the mask 1, preventing the photosensitive resin from being shaped into a predetermined pattern. Because of these reasons, it is difficult to form color filters of fine patterns directly on the solid state imagers.